Draughts account for around 15 to 20 percent of heat loss in most UK homes and can be the single biggest reason a well-heated flat still feels cold. Rented flats are especially vulnerable because tenants cannot install permanent insulation or replace windows, and landlords rarely invest in draught-proofing that mostly benefits the resident. The good news is that the five biggest heat-loss draughts in almost any flat are fixable by the tenant, reversibly, for under £60 total.
This guide covers the five draught sources ranked by impact, the specific reversible fixes for each, and where the strategy stops working (walls with real damp problems).
The five biggest cold-air draughts in a flat
- Front door gap. Most rental front doors were installed on a slightly warped frame and the bottom-edge or handle-side gap moves visible air. Biggest single fix in a hallway flat.
- Unused fireplace chimney. An open chimney creates a continuous updraft, pulling warm air out and cold air in through the flat. In older UK Victorian conversions this is a huge loss.
- Windows and window frames. Older single-glazed sashes leak everywhere. Even double-glazed windows lose heat around the frame seal if the seal has perished.
- Letterbox and cat flap. Direct opening from the exterior with a flimsy internal flap. Draught rushes through in cold weather.
- Extractor fans in bathroom and kitchen. The internal shutter often fails to close, leaving a permanent chimney-like hole to outside.
Every additional draught source (electrical sockets on exterior walls, floorboard gaps, keyholes) adds a smaller loss. The five above account for roughly 80 percent of the addressable draught loss in most flats.
Fix 1: The front door
Three-layer approach:
- Draught excluder brush screwed to the bottom of the door (7 to 15 pounds, £8 to £15). Two screws, five minutes. Cover the sweep width plus 20 mm each side.
- Foam or rubber P-strip around the door frame (£4 to £8 for a 10 m roll). Self-adhesive, presses flat against the door when closed. Choose P-strip over the cheaper E-strip; P compresses better and lasts longer.
- Draught excluder sausage (£10 to £20) at the base if the door is warped and cannot seal fully.
All three come off cleanly at end of tenancy. Combined cost £25 to £40; combined effect can be a 4 to 6°C jump in hallway temperature on a cold day.
Fix 2: The chimney
Only if the fireplace is genuinely unused and you have no plan to use it in the next year:
- Buy a chimney balloon (Chimney Sheep, Chimella, £20 to £30, one-time cost).
- Insert into the flue opening at reachable height above the fireplace.
- Inflate or expand until it seals the diameter.
- Attach the “chimney sealed – remove before lighting fire” tag it comes with, and hang it visibly on the fireplace itself.
Removes in 30 seconds if you ever want to reopen the fireplace. Single biggest heating-loss fix in most Victorian conversions.
Related: Winter Heating Savings Tips covers the behavioural side once the flat is properly sealed.
Fix 3: Windows
Two levels, escalating cost and effort:
- Foam window seal strips (£5 to £10 per window) applied to the frame not the glass. Compress as you close the window. Best for wooden sash windows that no longer seal fully.
- Peel-off shrink window film (£12 to £20 per window kit). Attach the film to the wooden frame with double-sided tape, shrink flat with a hairdryer. Creates a secondary glazing air pocket. Effective for single-glazed rooms and cold-frame double-glazing.
Both come off cleanly at end of tenancy. Window film in particular is transformative in single-glazed bedrooms; the room feels 2°C warmer without heating changing at all.
Fix 4: Letterbox
Cheap and quick:
- Internal letterbox brush and flap (£8 to £15). Screws to the inside of the door behind the existing metal letterplate.
Fits any standard letterplate. Almost invisible from outside. Fixes a surprisingly large winter draught for very little effort.
Fix 5: Extractor fan shutters
Bathroom and kitchen extractor fans often have a plastic shutter behind the outside grille that has failed. Two options:
- Check the outside shutter (needs looking outside; may need landlord). If broken, ask landlord to repair; it is a maintenance job.
- Fan-shaped magnetic vent cover (£10 to £15) fixed over the inside grille when the fan is not needed. Remove for cooking or bathing.
What draught-proofing does not fix
Do not confuse these:
- Damp. Sealing a flat that has a damp wall problem traps moisture and grows mould. Fix damp before sealing.
- Cold walls (thermal bridging). The wall itself losing heat is a different problem. Draught-proofing does not help; only internal insulation does, and that needs landlord permission.
- Cold floors. Floor draught in ground-floor flats needs different fixes (draught-proofed skirting boards, thicker carpet underlay).
Quick reference: the sub-£60 winter kit
| Item | Cost | Fits |
|---|---|---|
| Door bottom brush | £8-15 | Front door underside |
| P-strip foam roll | £4-8 | Door frames |
| Chimney balloon | £20-30 | Unused fireplace |
| Window film kit | £12-20 per window | Single-glazed or leaky frames |
| Letterbox brush | £8-15 | Any front door letterplate |
| Extractor cover | £10-15 | Bathroom / kitchen fan grille |
Where to start if you buy nothing else
The single highest-impact spend in a UK Victorian conversion is the chimney balloon (£20-30) if you have an unused fireplace. In a modern flat with no fireplace, start with the front-door bottom brush and letterbox brush (£16-30 combined). Both take under 30 minutes to install and pay back in one heating season.
Draught-proofing is not a full retrofit and it does not turn a cold flat into a passive house. It is the reversible, cheap, tenant-legal 15 percent that gets skipped precisely because it is so unglamorous. Do it once at the start of a tenancy and the flat is measurably warmer, quieter, and cheaper to heat for the rest of the lease.
What one weekend of draught-proofing feels like the following winter
Most tenants who install the kit above report the same experience: the flat feels noticeably quieter (draughts carry road noise) and warmer at the same thermostat setting. Bills drop within one full billing cycle, though the exact number varies by base efficiency and heating pattern. What does not change: the walls, the windows themselves, and the fundamental construction. Draught-proofing is the airtight layer on top of an unimproved fabric; it is a real improvement but not a retrofit.
Sources and further reading
Frequently asked questions
A well-sealed pre-1970s rental typically cuts heating bills 10 to 15 percent versus the same flat unsealed. Modern flats built after 2000 lose less to draughts and see smaller savings, more in the 3 to 8 percent range.
Yes for single-glazed windows in a cold room, especially north-facing bedrooms. A £15 kit for a standard sash raises the room temperature by 1 to 2°C and cuts condensation. Peel off in spring without residue if applied to the frame not the glass.
A chimney balloon is an inflatable plug that seals an unused fireplace. Chimneys are the single biggest cold-air draught in older UK flats. £20-30, install in 10 minutes, remove when the fireplace is next needed. Do not forget it is there and light a fire.
Not usually. Modern adhesive strips (P-strip, brush pile) use low-tack adhesive and peel off with heat from a hairdryer. Test on an inconspicuous area first if you are worried; brushes screwed to the door bottom leave two small holes but are usually landlord-approvable as maintenance.
